Our proposed research is aimed at clarifying the function of plasma lipoproteins in atherosclerosis. Our attention is directed at the various physicochemical and enzymatic factors that account for the retention and accumulation of swine and human plasma lipoproteins in the aorta. Using model systems, we will attempt to clarify alterations in the surface and interior properties of the lipoproteins taking place during their circulation and following their entry into the aorta. Furthermore, we will study the interactions of these lipoproteins with connective tissue components in the aorta, such as elastin, acid mucopolysaccharide, and collagen. Regarding the changes occurring in lipoproteins during the circulation, we will concentrate on lecithin-cholesterol acyltransferase. Concerning lipoprotein modifications following their entry into the aorta, we will determine the effects of proteolytic, lipolytic, lysosomal, and other enzymes. We intend to use both swine and human plasma lipoproteins in our research. Swine aortic tissue will serve as a source of various enzymes and of connective tissue components. The proposed study may indicate that the accumulation of lipids in atherosclerosis is influenced by changes in the physical state of lipoproteins and lipids and in their macro- and microenvironments. BIBLIOGRAPHIC REFERENCES: M. Janado, K. Shimada, N. Horie, and T. Nishida. Additional Evidence for Hydrophobic Bond Formation in the Adsorption of Sulfanilamide on Bio-Gel Beads. J. Biochem. 80, 69-71 (1976). Y.C. Kim, and T. Nishida. Nature of Interaction of Dextran Sulfate with Lecithin Dispersions and Lysolecithin Micelles. J. Biol. Chem. 252, 1243-1249 (1977).